We have been preparing a chemoarchitectonic atlas of the developing mouse brain. We have revealed a region in the forebrain of the E14 rat embryo which contains a large accumulation of CR-immunoreactivity (CR-IR). We believe this region is the little known "thalamic eminence" (TE). We have developed a method for the discrete dissection of this region in order to produce a cell culture system enriched in calretinin neurons. This system comprised approximately 40% of the total neuronal population of these cells. The effects of several neurotrophins on the neurite growth of calretinin-immunoreactive (CR-IR) neurons was investigated. Brain-derived neurotrophic factor (BDNF) significantly increased the number of CR-IR cells. BDNF also increased the number and length of secondary neurites. It therefore appears that BDNF increased the CR concentration in cells above the threshold of detection by immuno- histochemistry and also stimulates the sprouting of secondary CR-IR fibers.